xfs: overflow in xfs_iomap_eof_align_last_fsb

If extsize is set and new_last_fsb is larger than 32 bits, the
roundup to extsize will overflow the align variable. Instead,
combine alignments by rounding stripe size up to extsize.
Signed-off-by: Peter Watkins <treestem@gmail.com>
Reviewed-by: Nathaniel W. Turner <nate@houseofnate.net>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_iomap.c

@@ -52,7 +52,6 @@ xfs_iomap_eof_align_last_fsb(
 	xfs_extlen_t	extsize,
 	xfs_fileoff_t	*last_fsb)
 {
-	xfs_fileoff_t	new_last_fsb = 0;
 	xfs_extlen_t	align = 0;
 	int		eof, error;
 
@@ -70,8 +69,8 @@ xfs_iomap_eof_align_last_fsb(
 		else if (mp->m_dalign)
 			align = mp->m_dalign;
 
-		if (align && XFS_ISIZE(ip) >= XFS_FSB_TO_B(mp, align))
-			new_last_fsb = roundup_64(*last_fsb, align);
+		if (align && XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, align))
+			align = 0;
 	}
 
 	/*
@@ -79,14 +78,14 @@ xfs_iomap_eof_align_last_fsb(
 	 * (when file on a real-time subvolume or has di_extsize hint).
 	 */
 	if (extsize) {
-		if (new_last_fsb)
-			align = roundup_64(new_last_fsb, extsize);
+		if (align)
+			align = roundup_64(align, extsize);
 		else
 			align = extsize;
-		new_last_fsb = roundup_64(*last_fsb, align);
 	}
 
-	if (new_last_fsb) {
+	if (align) {
+		xfs_fileoff_t	new_last_fsb = roundup_64(*last_fsb, align);
 		error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);
 		if (error)
 			return error;